Healthy teenage years 'can delay breast cancer'

By Roger Highfield, Science Editor

12:01AM BST 24 Oct 2003

Exercise and healthy weight during teenage years can lead to a significant delay in the development of breast cancer, even among women with the highest genetic risk, according to a major study published today.

This is the first time a study has shown that exercise and weight control can influence cancer in women with a strong genetic predisposition.

Women who carry inherited mutations in the genes BRCA1 or BRCA2 have a lifetime risk of breast cancer of more than 80 per cent, as well as a high risk of ovarian cancer, according to the study, the most comprehensive to date.

The study of Ashkenazi Jewish breast cancer patients and their families, published by the New York Breast Cancer Study Group in the journal Science, also found that many women with these inherited mutations come from families with few if any reports of breast or ovarian cancer.

Even among women at very high risk, exercise and healthy weight as an adolescent delayed the onset of breast cancer, so that 90 per cent of the inactive group were diagnosed by their mid-50s, while it took until the age of 70 for the same proportion of the active group.

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"It was a surprise, but a source of hope, to learn that factors over which we have some control made a difference in the age at which these highest-risk women developed breast cancer," said Prof Mary-Claire King, the lead author, of the University of Washington in Seattle. "Women with inherited mutations were at extremely high risk but exercise and appropriate weight during their adolescent years clearly delayed the onset."

Prof Larry Norton, of the Memorial Sloan-Kettering Cancer Centre, said: "The possibility that lifestyle changes such as increased exercise and weight control could modify the impact of genetic risk has very intriguing implications, not only for BRCA-related cancers but for other breast cancers as well."

Up to 10 per cent of women who develop breast cancer have inherited a genetic mutation in BRCA1 or BRCA2 genes which play a role in helping to repair cell damage and prevent cancer.

Previous studies suggested widely varying estimates of breast cancer risk - from 25 per cent to 80 per cent - among women with these mutations; the overall risk for all women is about 10 per cent. To resolve these discrepancies, the team studied the genes of more than 2,000 people from families that each had one woman with breast cancer.